U.S. Pat. No. 4,801,051 is directed to a flow control device wherein a micro-axial adjustment of a valve needle which controls fluid flow through a nozzle is employed to compensate for changes in the working liquid viscosity. The valve length adjustment is achieved with a travel adjustment screw so as to either narrow or widen a gap between the valve and the valve seat thus creating commensurate adjustments in the fluid flow. The patent does not, however, teach or suggest a means of changing the valve at the machine when the valve is worn or is otherwise in need of replacement.
U.S. Pat. No. 4,588,163 is directed to a stem travel limiting apparatus wherein an internally threaded annular collar is engaged with a threaded stem. A locking ring is positioned over the collar so that it can exert a force over the collar sufficient to partially close the gap and to force the threads of the stem and collar into distortion. The patent does not teach a means of repositioning or replacing the stem at the equipment when the valve is worn or is otherwise in need of replacement.